The present invention, in some embodiments thereof, relates to microRNAs and, more particularly, but not exclusively, to the use of same for disease diagnosis, treatment and monitoring treatment.
Mood disorders such as major depression represent some of the most common and proliferating health problems worldwide effecting about 10% of the population. Despite many decades of research, the mechanisms behind depression onset, susceptibility and available therapies are only partially understood. Currently only about a third of patients respond to available treatments, therefore, there is a great need for better understanding of the pathology. The current dogma regarding the etiology of depression is of a complex interaction between environmental factors and genetics predisposition, suggesting a mechanistic role for epigenetic processes.
Serotonin (5HT) is a monoamine neurotransmitter produced in the brain by the raphe nucleus (RN), which project extensively throughout the brain to modulate variety of cognitive, emotional and physiological functions. The link between disregulated serotonergic activity and depression is well established [Michelsen K A. et al., Brain Res Rev (2007) 55(2):329-42]. The levels of 5HT, as well as the genetic circuitry in charge of it production, secretion, reuptake and deactivating, are dysregulated in depression. Furthermore, most currently available antidepressant drugs target the function of 5HT system related proteins, resulting in increased 5HT levels in the synapse [Krishnan V and Nestler E J, Nature (2008) 455: 894-902]. Available therapeutics require a long period of administration before relief of symptoms is observed.
MicroRNAs (miRs) are a subset of endogenous small (approximately 22 nucleotide) RNA molecules that repress gene expression post-transcriptionally. MiRs are transcribed as primary-miR molecules that are processed in the cell nucleus into precursor miRs with stem loop structures, which are exported to the cytoplasm where they are further processed into the active mature miRs. The mature miR is subsequently incorporated into the RNA-induced silencing complex and function primarily by binding to the 3′ untranslated regions (3′UTRs) of specific mRNA molecules. Binding occurs via the seed sequence, a 6-8 nucleotides sequence at the 5′ end of the miR, that base pairs to a complementary seed match sequence on the target mRNA 3′ UTR. Binding of a miR leads to direct mRNA destabilization or translational repression, ultimately resulting in reduced protein levels of target gene.
MiRs are abundant in the nervous system, and initial research has mainly focused on neurons in the context of development, cancer and neurodegenerative disorders and normal process such as plasticity [Kosik K S. Nat Rev Neurosci (2006) 7:911-20]. Additionally, it has been suggested that miRs play a role in psychiatric disorders such as schizophrenia, autism and also depression and anxiety, both in humans and in mouse models [Miller B H and Wahlestedt C, Brain Res (2010) 1338: 89-99]. Several studies have recently demonstrated the involvement of miRs in regulating 5HT related genes [Millan M J. Curr Opin Pharmacol (2011) 11(1):11-22] revealing the emerging role of miRs in the regulation of 5HT system and their potential association with depression related disorders.
U.S. Patent Application No. 20100222413 (to Stoffel M. et al.) disclose chemically modified oligonucleotides for modulating expression of microRNAs. U.S. 20100222413 further discloses methods for silencing microRNAs (e.g. miR-122, miR-16, miR-192 and miR-194) for the treatment of diseases of the central nervous system.